- JAEA has carried out “the project on the Long-term Assessment of Transport of Radioactive Contaminant in the Environment of Fukushima (F-TRACE project)” since the end of 2012. Radioactive caesium has been distributed by the fall out by Fukushima Dai-ichi Nuclear Power Plant (1F-NPP) accident, and forests in mountain areas have large amount of inventory of radioactive caesium and cover relatively large part of contaminated area of Fukushima. In this project, the transport behavior of radioactive caesium from the forests to biosphere and sea is evaluated by computer simulation based on the results of field observation and laboratory experiments. The results are used to predict evolution of effective dose of the residents in the affected area due to the transport, specify the dominant pass way of caesium, and propose effective methodology to constrain the transport along the pass way.
- The field investigations were conducted focusing on the river transport including forest, rivers, dams, reservoirs, and estuary. The data displayed here were based on the river survey results of soils.
- Measurements were conducted from February 2013 to March 2013, October 2013 to December 2013, November 2014 to January 2015, November 2015, December 2015, October 2016 to January 2017.
- Sampling points were selected form the same river cross-section but characterized with different flows, different deposition condition, and different dose rate. The soils at different depths were sampled with the scraper plate method which the IAEA recognized to be a standard soil sampling method by depths.
- The soil sample taken from each depth was well stirred and its designated amount was encapsulated in a V-1 container. The sediment samples in the V-1 containers were provided for the quantitative analysis of radioactive cesium using the fixed type germanium semiconductor detector.
- Radioactivity concentrations, errors, and detection limits described here were decay corrected values of the sampling date.
- "ND" as a measured value and "-" as an error indicate the radioactivity concentration measured was below the detection limit.
